The present invention relates to control apparatuses for hybrid electric vehicles.
Examples of known hybrid electric vehicles include one in which an electric current is supplied to a motor from each of a battery and a generator driven by an engine, and a driving wheel is driven by driving torque outputted from the motor.
In such a hybrid electric vehicle, when an electric current is continuously supplied to a motor from a battery, the temperature of the battery is increased. There is apprehension that an excessive increase in battery temperature will cause degradation of the battery. To cope with this, when the battery temperature is equal to or higher than a preset threshold temperature, the electric current supplied to the motor from the battery is suppressed (or motor torque is suppressed), thereby suppressing an increase in battery temperature.
However, such torque suppression affects traveling performance of a vehicle, and thus has room for improvement.
Further, as a technique for preventing battery degradation, there is proposed a technique (related art) in which a depth of discharge of a battery is calculated based on the temperature of the battery, and when the rate of increase in battery temperature is high, a generator is activated in a state where the depth of discharge is low (see Japanese Patent No. 3707206).
However, in the above related art, an engine is started to activate the generator in the state where the depth of discharge is low; thus, although an increase in battery temperature can be suppressed, there is apprehension that the engine might be uselessly started, thereby reducing fuel efficiency.